Cathodic Behaviour of Dicationic Imidazolium Bromides: The Role of the Spacer

Abstract

The cathodic reduction of dicationic imidazolium bromides, whose spacer is either an aliphatic chain or a xylyl group, leads to the formation of the corresponding N‐heterocyclic carbenes (NHCs), which were isolated as the corresponding thiones, after reaction with elemental sulfur. The behaviour of the dications was compared with the corresponding monocations. The behaviour of dicarbenes depends on the nature of the spacer. This study evidenced that dicarbenes deriving from xylyl dications are less stable than the corresponding aliphatic ones (giving lower yields in thiones), due to a debenzylation reaction. On the other hand, the yields in thiones starting from aliphatic dications are higher than the corresponding monocations, suggesting a cooperative reduction at the electrode of the two imidazolium moieties. The cathodic process was confirmed using the co‐electrogenerated hydrogen to reduce 2,2,2‐trifluoroacetophenone to the corresponding alcohol.

Electrochemical Generation of N‐Heterocyclic Carbenes for Use in Synthesis and Catalysis

“…As NHCs are most often produced chemically via base deprotonation of the corresponding azolium salt, base sensitive groups within the ligand architecture are typically not tolerated using these synthetic methods. The electrochemical synthesis of NHCs also proceeds from the corresponding azolium salt, but in this case the azolium is reduced to the carbene at the cathode with hydrogen as the only by‐product [10] . An electrochemically synthesized NHC is thereby referred to as electrogenerated.…”

pH-Responsive Nanostructures Based on Surface Active Fatty Acid-Protic Ionic Liquids for Imiquimod Delivery in Skin Cancer Topical Therapy

“…Ionic liquids (ILs) are organic salts with melting points below 100 °C which are endowed with unique physico-chemical properties such as low flammability, negligible vapor pressure, high thermal and chemical stability, and wide electrochemical window [ 24 , 25 , 26 , 27 , 28 ]. By careful selection of the constituting ions, the features of interest of an IL can be tailored to a given application.…”

An insight into the intermolecular vibrational modes of dicationic ionic liquids through far-infrared spectroscopy and DFT calculations

“…For instance, it has been found that some DILs are characterized by lower polarity and different structural organizations, 21 higher thermal stabilities, 22 lower ecotoxicities, 23 higher activity in the cycloaddition of CO 2 to epoxides, 24 higher or lower cathodic reductions, depending on the type of spacer. 25 The physico-chemical properties of ILs, and accordingly their potential applications, are strictly governed by the type and strength of the interaction between the constituent ions. Intermolecular forces between cation and anion determine the presence of expanded network structures such as larger clusters or ion-pairs in the liquid phase.…”